1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * DT idle states parsing code.
4  *
5  * Copyright (C) 2014 ARM Ltd.
6  * Author: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
7  */
8 
9 #define pr_fmt(fmt) "DT idle-states: " fmt
10 
11 #include <linux/cpuidle.h>
12 #include <linux/cpumask.h>
13 #include <linux/errno.h>
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/of.h>
17 
18 #include "dt_idle_states.h"
19 
20 static int init_state_node(struct cpuidle_state *idle_state,
21 			   const struct of_device_id *match_id,
22 			   struct device_node *state_node)
23 {
24 	int err;
25 	const char *desc;
26 
27 	/*
28 	 * CPUidle drivers are expected to initialize the const void *data
29 	 * pointer of the passed in struct of_device_id array to the idle
30 	 * state enter function.
31 	 */
32 	idle_state->enter = match_id->data;
33 	/*
34 	 * Since this is not a "coupled" state, it's safe to assume interrupts
35 	 * won't be enabled when it exits allowing the tick to be frozen
36 	 * safely. So enter() can be also enter_s2idle() callback.
37 	 */
38 	idle_state->enter_s2idle = match_id->data;
39 
40 	err = of_property_read_u32(state_node, "wakeup-latency-us",
41 				   &idle_state->exit_latency);
42 	if (err) {
43 		u32 entry_latency, exit_latency;
44 
45 		err = of_property_read_u32(state_node, "entry-latency-us",
46 					   &entry_latency);
47 		if (err) {
48 			pr_debug(" * %pOF missing entry-latency-us property\n",
49 				 state_node);
50 			return -EINVAL;
51 		}
52 
53 		err = of_property_read_u32(state_node, "exit-latency-us",
54 					   &exit_latency);
55 		if (err) {
56 			pr_debug(" * %pOF missing exit-latency-us property\n",
57 				 state_node);
58 			return -EINVAL;
59 		}
60 		/*
61 		 * If wakeup-latency-us is missing, default to entry+exit
62 		 * latencies as defined in idle states bindings
63 		 */
64 		idle_state->exit_latency = entry_latency + exit_latency;
65 	}
66 
67 	err = of_property_read_u32(state_node, "min-residency-us",
68 				   &idle_state->target_residency);
69 	if (err) {
70 		pr_debug(" * %pOF missing min-residency-us property\n",
71 			     state_node);
72 		return -EINVAL;
73 	}
74 
75 	err = of_property_read_string(state_node, "idle-state-name", &desc);
76 	if (err)
77 		desc = state_node->name;
78 
79 	idle_state->flags = CPUIDLE_FLAG_RCU_IDLE;
80 	if (of_property_read_bool(state_node, "local-timer-stop"))
81 		idle_state->flags |= CPUIDLE_FLAG_TIMER_STOP;
82 	/*
83 	 * TODO:
84 	 *	replace with kstrdup and pointer assignment when name
85 	 *	and desc become string pointers
86 	 */
87 	strncpy(idle_state->name, state_node->name, CPUIDLE_NAME_LEN - 1);
88 	strncpy(idle_state->desc, desc, CPUIDLE_DESC_LEN - 1);
89 	return 0;
90 }
91 
92 /*
93  * Check that the idle state is uniform across all CPUs in the CPUidle driver
94  * cpumask
95  */
96 static bool idle_state_valid(struct device_node *state_node, unsigned int idx,
97 			     const cpumask_t *cpumask)
98 {
99 	int cpu;
100 	struct device_node *cpu_node, *curr_state_node;
101 	bool valid = true;
102 
103 	/*
104 	 * Compare idle state phandles for index idx on all CPUs in the
105 	 * CPUidle driver cpumask. Start from next logical cpu following
106 	 * cpumask_first(cpumask) since that's the CPU state_node was
107 	 * retrieved from. If a mismatch is found bail out straight
108 	 * away since we certainly hit a firmware misconfiguration.
109 	 */
110 	for (cpu = cpumask_next(cpumask_first(cpumask), cpumask);
111 	     cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpumask)) {
112 		cpu_node = of_cpu_device_node_get(cpu);
113 		curr_state_node = of_get_cpu_state_node(cpu_node, idx);
114 		if (state_node != curr_state_node)
115 			valid = false;
116 
117 		of_node_put(curr_state_node);
118 		of_node_put(cpu_node);
119 		if (!valid)
120 			break;
121 	}
122 
123 	return valid;
124 }
125 
126 /**
127  * dt_init_idle_driver() - Parse the DT idle states and initialize the
128  *			   idle driver states array
129  * @drv:	  Pointer to CPU idle driver to be initialized
130  * @matches:	  Array of of_device_id match structures to search in for
131  *		  compatible idle state nodes. The data pointer for each valid
132  *		  struct of_device_id entry in the matches array must point to
133  *		  a function with the following signature, that corresponds to
134  *		  the CPUidle state enter function signature:
135  *
136  *		  int (*)(struct cpuidle_device *dev,
137  *			  struct cpuidle_driver *drv,
138  *			  int index);
139  *
140  * @start_idx:    First idle state index to be initialized
141  *
142  * If DT idle states are detected and are valid the state count and states
143  * array entries in the cpuidle driver are initialized accordingly starting
144  * from index start_idx.
145  *
146  * Return: number of valid DT idle states parsed, <0 on failure
147  */
148 int dt_init_idle_driver(struct cpuidle_driver *drv,
149 			const struct of_device_id *matches,
150 			unsigned int start_idx)
151 {
152 	struct cpuidle_state *idle_state;
153 	struct device_node *state_node, *cpu_node;
154 	const struct of_device_id *match_id;
155 	int i, err = 0;
156 	const cpumask_t *cpumask;
157 	unsigned int state_idx = start_idx;
158 
159 	if (state_idx >= CPUIDLE_STATE_MAX)
160 		return -EINVAL;
161 	/*
162 	 * We get the idle states for the first logical cpu in the
163 	 * driver mask (or cpu_possible_mask if the driver cpumask is not set)
164 	 * and we check through idle_state_valid() if they are uniform
165 	 * across CPUs, otherwise we hit a firmware misconfiguration.
166 	 */
167 	cpumask = drv->cpumask ? : cpu_possible_mask;
168 	cpu_node = of_cpu_device_node_get(cpumask_first(cpumask));
169 
170 	for (i = 0; ; i++) {
171 		state_node = of_get_cpu_state_node(cpu_node, i);
172 		if (!state_node)
173 			break;
174 
175 		match_id = of_match_node(matches, state_node);
176 		if (!match_id) {
177 			err = -ENODEV;
178 			break;
179 		}
180 
181 		if (!of_device_is_available(state_node)) {
182 			of_node_put(state_node);
183 			continue;
184 		}
185 
186 		if (!idle_state_valid(state_node, i, cpumask)) {
187 			pr_warn("%pOF idle state not valid, bailing out\n",
188 				state_node);
189 			err = -EINVAL;
190 			break;
191 		}
192 
193 		if (state_idx == CPUIDLE_STATE_MAX) {
194 			pr_warn("State index reached static CPU idle driver states array size\n");
195 			break;
196 		}
197 
198 		idle_state = &drv->states[state_idx++];
199 		err = init_state_node(idle_state, match_id, state_node);
200 		if (err) {
201 			pr_err("Parsing idle state node %pOF failed with err %d\n",
202 			       state_node, err);
203 			err = -EINVAL;
204 			break;
205 		}
206 		of_node_put(state_node);
207 	}
208 
209 	of_node_put(state_node);
210 	of_node_put(cpu_node);
211 	if (err)
212 		return err;
213 
214 	/* Set the number of total supported idle states. */
215 	drv->state_count = state_idx;
216 
217 	/*
218 	 * Return the number of present and valid DT idle states, which can
219 	 * also be 0 on platforms with missing DT idle states or legacy DT
220 	 * configuration predating the DT idle states bindings.
221 	 */
222 	return state_idx - start_idx;
223 }
224 EXPORT_SYMBOL_GPL(dt_init_idle_driver);
225